This invention relates to an assembly which is detachably mounted to a body fluid-monitoring system for laboratory testing of a body fluid such as blood, wherein the assembly has a lancet and a means for collecting and detecting the body fluid. This invention also relates to a body fluid-collecting and detecting unit for use in such assembly, and a body fluid-monitoring system having such an assembly detachably mounted thereto.
With the increase in the number of patients suffering from diabetes, self-monitoring of blood glucose wherein the patient can daily monitor his or her blood glucose level has been highly recommended. In view of such situation, various systems wherein a lancet and a glucose meter are integrated have been disclosed for ease of the blood glucose self-monitoring and to enable hygienic measurement. Such systems are disclosed, for example, in JP-A 6-339473, JP-A 9-276235, and U.S. Pat. No. 4,787,398.
In the system of the type disclosed in JP-A 6-339473, the lancet mechanism and the detection mechanism are separate, and the lancet unit including the puncture needle and the detection unit including the test strip should be separately mounted on the monitoring system, and the operation is cumbersome.
JP-A 9-276235 and U.S. Pat. No. 4,787,398 proposes a body fluid-monitoring system wherein the lancet mechanism and the detection mechanism are integrally assembled.
The blood glucose meter disclosed in JP-A 9-276235 comprises a lancet, a tourniquet for compressing the finger, and a means for detecting the target component in the blood and displaying the results, accommodated in a housing. In this glucose meter, collection of the required amount of the blood is enabled by the use of the tourniquet, and as a consequence, this system is associated with the risk of infection by the blood that adheres to the tourniquet when the finger is pulled out through the tourniquet after the blood collection.
JP-A 9-276235 also discloses use of a disposable cartridge wherein a puncture needle and an electrode coated with an enzyme ink are accommodated. JP-A 9-276235, however, is silent about sterilization of the puncture needle before its use. In JP-A 9-276235, the puncture needle and the electrode coated with the enzyme ink are arranged adjacent to each other, and sterilization of the puncture needle should be quite difficult once the cartridge is accommodated in the cartridge. Assembly of the cartridge after sterilizing the puncture needle, on the other hand, is quite nonproductive since a clean room is required for such operation.
U.S. Pat. No. 4,787,398 proposes a monitoring system wherein a unit provided with a lancet having a puncture needle and a detection means having a test strip can be mounted on the main body of the monitoring system, and wherein the operation is thereby simplified. This system also suffers from the difficulty of sterilization as in the case of JP-A 9-276235, and sterilization of the unit before its use is associated with the risk of denaturing of the reagents immobilized on the test strip. Therefore, it has been difficult to deliver a product wherein sterilization of the puncture needle is maintained until the use of the product.
The self-monitoring of blood glucose is normally conducted by using a lancet and a glucose meter. To be more specific, the lancet having a puncture needle or a blade on its tip is first used to collect the blood of required volume by pricking the finger tip with the lancet and milking or squeezing the skin around the puncture site to ensure the formation of the blood droplet of required amount. The lancet is held by the hand which is not bleeding in the step of blood collection. The lancet is then replaced with the glucose meter for the measurement of the blood glucose. Such change of the device should be conducted while the blood is flowing out from the punctured site, and this procedure is associated not only with inconvenience of the operation but also with unfavorable sanitary conditions.
Use of a body fluid-collecting cartridge is also proposed including the type wherein the blood is dropped on the test strip in the cartridge, the type wherein the blood is guided to the test strip by capillary action, and the type wherein the blood is once introduced into a reservoir defined in the cartridge and then guided to the test strip by capillary action. See, for example, JP-A 4-264246, JP-A 7-55801 and JP-A 247946.
The type wherein the blood is dropped on the test strip in the cartridge is associated with the problem of inconsistent measurement value since the time interval between the blood collection and mounting of the cartridge is not constant.
The type wherein the blood is guided to the test strip by capillary action is also associated with various demerits. For the purpose of reducing the burden of the patient, the interior volume of the capillary is minimized to reduce the amount of the blood remaining in the capillary after the detection. Such reduction in the volume of the capillary results in the reduced size of the inlet of the capillary, and introduction into the capillary of the blood becomes difficult. In addition, when the area surrounding the capillary inlet erroneously becomes in contact with the blood, sucking of the blood into the capillary is impeded. The situation is the same even if a reservoir is provided in the cartridge unless an appropriate guiding structure is provided in the area surrounding the inlet. Moreover, when such reservoir is in the same plane as the main body of the cartridge, there is always some risk of blood leakage from the gap between the finger and the reservoir due to the finger print unless the finger is very tightly pressed against the cartridge, and such blood leakage is likely to result in the blood adhesion to the back surface of the cartridge, and also, increase in the amount of the blood necessary for the measurement. On the other hand, when the blood volume collected by the lancet is insufficient, the blood will never reach the test strip. The measurement is, therefore, unreliable and unsanitary.
In view of such situation, there is a strong demand for a body fluid-collecting cartridge which is capable of reliably sucking the collected body fluid into its interior with no adhesion on the exterior surface, and wherein collection of minimum necessary amount of the body fluid is required.